Corrosion inhibitors



Feb 7, 1951 H. M. ZIMMERMAN ETAL 2,971,044

CORROSION INHIBITORS Original Filed Jan. 3, 1956 INVENTORS' HERMAN M. ZIMMERMNNA ROBERT A. POWERS ATTORNEY United States Patent C CORROSIGN INHIBITORS Herman M. Zimmerman and Robert A, Bowers, Lalre;`

wood, Ohio, assignors` to UnionA Carbide Corporation, acorporationof NewYork Original application Jan. 3, '1956, Ser. No. 557,013, now Patent No. 2,900,434, dated Aug. 18, 1959. Divided and this application June. 9, 195,9, Ser. No. 8 1Sl,034f

This invention -relates to corrosion inhibitors adapted for use in primary cells, particularly dry cells, and to cells containing such inhibitors.

4Open circuit corrosion of dry cell anodes when the,

pacity. To cite but one. example of its seriousness, in

the case of telephone cells, )approximately 50 percent as much zinc is removed from the anode by wasteful c orf` rosion as by useful, current-producing, anodic` attack.

To prevent or lessen such corrosion, many expedients have been suggested and tried, including the introduction in various ways of mercury, mercury saltsand chromie salts in the cell.

Among the disadvantages of using mercury or mercury salts alone as cell corrosion inhibitors are the following:

(l) Zinc possesses metalimpurities having low hydrogen overvoltage, which tend to accumulate Von the anode surface during operation, with the net result that the overvoltage of the amalgam surface is lowered while the corrosion rate increases.

(2) The effectiveness of amalgamation is limitedV by the extent to which air can be excluded from the cell.

(3.) As corrosion is a surface reaction, only that mercury present at the anode-electrolyte interface is effective in reducing corrosion.

(4) Mercury must be uniformly distributed at the anode surface. Non-uniform amalgamation can arise in many ways in `a dry cell, and lead to high corrosion rates.

yBecause ofits embrittling eiect on conventional anodic materials, only very small amounts of mercury can vbe used. This is true regardless of whether mercury or mercurio salts are employed.

Chromate inhibitors often prove unsatisfactory, as these are aiected by the presence and nature of cell paste, and often lose their effectiveness during operation.

Previous work using cationic organic compounds as dry cell corrosion inhibitors has `shown them to be unsatisfactory in that they tend to form high resistance anode films or -react with cell components, although wasteful anode corrosion may be low. f

. Lately it has been recognized that marked improvements in dry cell behavior with respect to corrosion inhibition can be obtained with inhibitors having several technical characteristics.

v( 1) Corrosion inhibiting materials should not react detrimentally with either electrolyte or` cell mix.

(2) These should be of such form as always to .be available at the yamide in :a proper concentration.

`(3) These should `inhibit wasteful corrosion without reducing the suede effectiveness.

.In line with. this realization and with 4a` viewite Dliyiataa prior art limitations, the principal object 0f` the Plnt 2,971,044 Patented Feb. 7, 196l ICC 2 invention is to provide corrosion inhibitors having novel and improved characteristics.

A further object of the invention is to provide a dry cell havingsubstantially improved properties attributable to the incorporation therein of the corrosion inhibitors of the invention.

Seeking to attain these objects, we have discovered that non-ionic surface active compounds made by` the addition of ethylenic oxide compounds to hydroxyl-bearrigzcompounds, effectively inhibit wasteful corrosion by raising the hydrogen overvoltage at the anode of the cells in which they are incorporated without adversely affecting normal cell performance. g

In the drawings:

Fig. l is a sectional elevational view of a conventional paste-lined cell containing the compounds of the invention;

Fig. 2 is a sectional elevational View of a film-lined cell having the herein-disclosed additives;

Fig. 3 illustrates an external cathode cell to which the corrosion inhibitors of this invention have been added; and

Fig. 4 is a sectional elevational view of a flat-type or stacked cell with the compounds of the invention.

The addition compounds which successfully perform in the practice of the invention generally possess the formula R.-O(R)n-R, where R stands for alkyl, aryl or aryl alkyl radicals, where R may be Yeither hydrogen or a grouping similar to R, R is an alkoxy radical such as ethoxy or propoxy, and n may be any number between 1 and 50. These compounds` are essentially linear polymers having wetting characteristics. 'Their inhibiting properties result from high hydrogen overvoltage created on the anode surface.

Examples of the above compounds with their effect on hydrogen overvoltage are presented in Table I.

Virtually all non-ionic surfactants of this type can raise the hydrogen overvoltage. Maximum overvoltage eifects result, however, from polyoxyethylated polynuclear aromatic phenols and alkyl aryl phenols. As little as 0.05 percent by weight of electrolyte or anode-con tacting media of` these materials suice to satisfactorily prevent wasteful cell corrosion.

'I'he corrosion inhibitors of this invention may be used alone or mixed.

' The corrosion inhibiting compounds of the invention mjay be incorporated in a cell by mixing with electrolyte or `with the depolarizing mix, or in conjunction with the separator` paste or film liner. Their effectiveness, however, is not:y affected by the method of introduction, as long as they are rendered immediately available to the anode surface.

To provide an understanding Qf the, ini/eaten, and far espasmos. it will he describe@ mainly by illustrations GIOCO 3 of the performance of two compounds of the non-ionic type. The first of these, known as parahydroxydiphenyl polyethylene oxide, also is known as paraphenyl phenoxy polyethylene glycol, hereinafter is referred to as PPPG.

This material is made by the addition of thirteen equivalents of ethylene oxide to one equivalent of parahydroxydiphenyl. Its nominal structure is as follows:

The second compound described is known as Neutronyx-600, and is characterized as an alkylphenol polyglycol ether. This material is prepared by reacting approximately nine and one-half moles of ethylene oxide with one mole of nonylphenol. l

Other specific materials of the same general type which have been tested and found to be suitable corrosion vinhibitors for dry cell use are:

(l) Polyglycol ether of l-naphthol (containing 11 equivalents of ethylene oxide).

(2) Polyglycol ether of Z-naphthol (containing 12 (7) `Polyglycol ether of phenol (containing 8 equiva= lents of ethylene oxide).

(8) Polyglycol ether o f di(2ethyl hexanol) (contain ing 13' equivalents of ethylene oxide).

(9) Polyglycol etherA of 2,6,8-trimethyl-4-nonyl(containing 8 equivalents of ethylene oxide). (10) .Glycol ether of octylphenol (containing 1 equivalent of ethylene oxide).

(11) Polyalkyl ether of dodecylphenol (containing 75 weight percent of mixed ethylene and Ypropylene oxides). Referring again to the general formula above, it is seen that R may stand for the residue of an initially hydroxylic compound.

Fig. l represents a conventional dry cell having a container anode, preferably of zinc l0, an insoluble cathode, preferablyof carbon 12, an electrolyte-wet depolarizing mix consisting of manganese dioxide 14 and cereal paste 16 intermediate theanode and cathode@ The'ce'real paste,

in this case, contains about 0.05 percent by weight of pphenyl phenoxy polyethylene glycol 18.

Fig. 2 is a conventional film-lined D-size round cell having a consumable container anode 20, preferably of zinc, an insoluble cathode 22, usually of carbon, an elec-.'- trolyte-wet, depolarizing mix 24 and an anode-contacting film 26 intermediate the anode and cathode. In this case the film has been modified by the incorporation therein of about 0.05 percent PPPG.

To incorporate PPPG in D-size round cells, the standard procedure for making anode-contacting films was slightly modified. Two and three-tenth grams of PPPG liquid were placed in hot, rapidly agitated, distilled water.

To thisv stirred solution was added 9.52 grams of wate1"- Stirring was consoluble 4000 cps. methyl cellulose. tinued until all the methyl cellulose was wet. 'I `he re-v sulting solution was thencooled in an ice bath with continued stirring to maintain a uniform thickness, and .until all the methyl cellulose dissolved. The solution was then poured on to a horizontal 300Y square inch glass plateA provided with a vremovable brim of plastic tape, and alsuch as wrapping paper, a cathode 32 of electrically con-y (6) Polyglycol ethers of octylphenol (containing ap- 30 proximately 3, 5, 7 or 9 equivalents of ethylene oxide,

amm@

solution and dried film composition and cell usage of anode films containing mercury and PPPG as zinc corrosion inhibitors for use in D-size cells.

Table II Film Identification Hg Control "PPPG" Solution Composition: Water grams.- 600 600 4,000 cos. water-soluble methyl cellulose--. 9. 52 9. 52 PPG none 2. Mercurio chloride 0. 75 none Total grams som/300 sq. in. plate 610. 27 611. 82

Film 'Composition/sq. in. Dry Anode Film: 4,000 cps. water-soluble methyl cellulose milligrams-. `31. 75 31. 75 PPPG 7. 65 Mercurio chloride 2. 50

FILM USED PER D-SIZE CELL Total film area per cell. 10.828 sq. in.. Total film size ner cell" 2% x 4% in. Total active film area/cell. 7.25 sq. in. -Total active film size/cell 111%@ x 4 in.

Total film thickness 0.0015 in.

Fig. 3 shows an external cathode cell comprising a non-corrodible tube 30, composed of fibrous material d'uctive carbon composition molded in situ, an anode 34,

preferably composed of zinc, centrally located in the.

- theanode 34 and the cathode 32 at 36. The electrolyte in this instance contains about 0.05 percent by weight of PPPG.

" The attype battery of Fig. 4 comprises an outer con tainer containing a plurality of thin dry cells, such as 4 2, jcomposed of an electrolyte-wet depolarizing mix 43,

PPPGl v In the above cell, as in previous Iones,'the additive of theinvention may be varied in accordance with the scope Again the quantity of additives may i be modified without departing from the scope of the' At least' 10 percent less zinc may be used if-thev instant for using pure zinc in cell constructions.

an--anode-contacting film 44, a zinc anode 46 and a car-v bon cathode 48. lThe electrolyte has been modified accordance with the method of the invention, by the addi?.

tion thereto of 0.05 percent by weight thereof of'.

of the invention.

lt is apparent that the use of PPPG obviates the need Accordingly, thismaterial may be substituted for mercury. A poorer grade or thinner gage of zinc may be incorporated in cell constructions toreduce cost and to conserve materials scarce in critical times, if the organic inhibitors are used.

inhibitors are employed` Results comparable with those discussed for film lined cells were obtained also with D-size paste-filled cells, wherein eight and one-half milligrams of another effective agent, Neutronyx-600, per ten milliliters of paste have been added.

The disappearance of external indications of corrosion (perforation of zinc cans) and the smoother surface of the active inside surface indicated that the inhibitor Was extremely effective for reducing general Zinc corrosion as well as eliminating areas of excessive corrosion up to ages of 24 months.

The experiments with Neutronyx-OO olfer evidence that the benefits derived from non-ionics such as PPPG and Neutronyx does not reside mainly in their function as wetting agents.

The exact mechanism whereby the desired effects obtain is not known. The interaction between PPPG and zinc affords a hypothesis. Taking electron diffraction patterns of an abraded zinc surface before and after Contact with a l percent solution of PPPG in benzene, it was observed that a definite amount of PPPG is firmly adsorbed by the zinc surface. The amount thus retained appears less than a full mono-layer, and is oriented with respect to the metal surface. This and other data indicate that PPPG is both chemically and physically adsorbed by zinc, and the observed increase in hydrogen overvoltage of zinc may be attributed to such an adsorbed layer. However, regardless of any theory of operation, our experiments highlighted in the present disclosure have proven that the service life of cells is very materially increased for any service in which shelf life is an important factor.

The inhibitors of this invention find successful employment in various types of primary cell structures. Naturally, for best performance, optimum variations may be made from the foregoing disclosure without departing from the spirit and scope of the instant invention.

This application is a division of our co-pending application Serial No. 557,013, filed January 3, 1956, now Patent No. 2,900,434.

What is claimed is:

1. In combination in a primary dry cell having a consumable anode, an insoluble cathode, an electrolyte-wet depolarizing mix and at least one organic corrosion inhibitor in contact with said anode, said organic inhibitor being defined by the formula wherein R is at least one radical selected from the group which consists of alkyl, aryl and aryl alkyl radicals, R is an alkoxy radical, n is any number between 1 and 50, and R is at least one radical selected from the group which consists of hydrogen, alkyl, aryl and alkyl aryl radicals.

2. In combination in a primary cell having a consumable anode, an insoluble cathode, an electrolyte-wet depolarizing mix, separator means intermediate said anode and cathode, said separator means containing an organic corrosion inhibitor in contact with said consumable anode, said organic inhibitor being defined by the formula wherein R is a radical selected from the group consisting of alkyl, aryl and aryl alkyl, R' is an alkoxy radical and n is a number between l and 50, and R is at least one radical selected from the group which consists of hydrogen, alkyl, aryl and alkyl aryl radicals.

3. In combination in a primary cell having a zinc anode, a carbon cathode, a depolarizer mix consisting of manganese dioxide and at least one organic corrosion inhibitor in contact with said zinc anode, said organic inhibitor being defined by the formula wherein R is at least one radical selected from the group consisting of alkyl, aryl, and aryl alkyl radicals, R' is an ethoxy radical and n is a number between l and 50, and R is at least one radical selected from the group which consists of hydrogen, alkyl, aryl and alkyl aryl radicals.

4. In combination in a primary dry cell having a zinc anode, an electrolyte-wet manganese dioxide depolarizer mix, a carbon cathode and corrosion inhibiting means consisting of p-phenyl phenoxy polyethylene glycol dispersed in said cell, contacting said zinc anode.

5. In combination in a primary dry cell having a zinc anode, carbon cathode, an electrolyte-wet manganese dioxide depolarizer mix, separator means intermediate said anode and cathode, said separator means containing pphenyl phenoxy polyethylene glycol to inhibit wasteful corrosion of said zinc anode.

6. In combination in a primary cell having a zinc anode, an insoluble cathode, an electrolyte-wet depolarizing mix consisting of manganese dioxide, cereal paste intermediate said anode and cathode, said cereal paste containing p-phenyl phenoxy polyethylene glycol to inhibit wasteful corrosion of said zinc anode.

7. In combination in a primary cell having a zinc anode, an insoluble cathode, a depolarizing mix consisting of manganese dioxide and an electrolyte containing p-phenyl phenoxy polyethylene glycol to inhibit wasteful corrosion of said zinc anode.

8. In combination in a primary cell having a zinc anode, an insoluble cathode, a depolarizing mix consisting of manganese dioxide and an electrolyte containing at least about 0.05 percent by weight of an alkyl-phenyl polyglycol ether.

9. In combination in a primary cell having a zinc anode, a cathode, a depolarizing mix consisting of manganese dioxide, and an electrolyte containing at least about 0.05 percent by weight of a polyoxyethylated polynuclear aromatic phenol to inhibit the wasteful corrosion of said zinc anode.

References Cited in the file of this patent UNITED STATES PATENTS 2,900,434 Zimmerman et al. Aug. 18, 1959 

1. IN COMBINATION IN A PRIMARY DRY CELL HAVING A CONSUMABLE ANODE, AN INSOLUBLE CATHODE, AND ELECTROLYTE-WET DEPOLARIZING MIX AND AT LEAST ONE ORGANIC CORROSION INHIBITOR IN CONTACT WITH SAID ANODE, SAID ORGANIC INHIBITOR BEING DEFINED BY THE FORMULA 